The present invention relates to an illumination unit using LEDs (Light Emitting Diodes) as a light source, and to a display apparatus using the same as a back light.
The illumination unit using an LED, i.e., a light emitting element, as a light source is used as a back light of a display apparatus with a transmission type display device, such as a liquid crystal display panel (LCD), and is widely put into practical use.
As the configuration of the illumination unit used as a back light, a configuration using an LED as a light source and a light guide plate for guiding the light emitted from the LED to an LCD side as a surface light source is known.
In such configuration, the light incoming from the light source travels inside the light guide plate by total internal reflection or the like, and is scattered by a diffusion/light guide pattern provided on the surface of the light guide plate, and is extracted from the surface of the light guide plate. At this time, in the vicinity of the light source (the vicinity of the light incident portion) of the light guide plate, the intensity of light locally increases as compared with other portions and the so-called uneven brightness is generated. As a conventional art for reducing such uneven brightness, it is known that a light shielding member or a light reflective/absorbing member is provided in the vicinity of a light source of the surface of a light guide plate, as described, for example, in JP-A-2005-117023 and JP-A-2003-242817.
Moreover, with regard to a difference in brightness between the end and the center of a light guide plate caused by neighboring reflections, it is known that as described, for example, in JP-A-2005-5067, a light guide pattern is varied between the end and the center of the light guide plate to suppress the uneven brightness.
Furthermore, with regard to the uneven brightness generated in the vicinity of a light source (the vicinity of a light incident portion) of a light guide plate as described, for example, in WO2010041499, an example and the like are known, in which the uneven brightness is reduced as a layered structure, wherein a light guide plate is split into a plurality of stages and portions in the vicinity of a light source of each light guide plate are diagonally overlapped.